It wouldn't have mattered too much ultimately.
IA64 - Sure, they wanted people to migrate to it, but even on the server it never got traction. Heck, Intel even admitted they had to neuter their other chips to make it look good! Their x86 chips perform far better. IA64 would have ONLY worked if they were able to make native performance 2-3x better than the *best* x86 implementation. That wasn't going to happen. They'd have tried to bring it to the PC for few years, and find out no one wants it. They'd have canned it, just a bit later than without AMD.
Netburst would have still ran into heat density issues. It's just unavoidable. They had to switch not just because of competition but because it wasn't feasible. People would have stopped buying it eventually. We might have seen Tejas at 150W, and performing barely better at 5GHz than Prescott at 4GHz.
You'd still see them struggling to enter mobile. If ANYTHING, AMD prepared Intel better for mobile, because imagine if 2006 was Netburst based Tejas rather than Core 2, and the Core 2 arch was in 2008. Rather than seeing Atom focus in 2010, it could have been in 2012. Atom Tablets wouldn't have seen its foot in the door.
Imagine a fledgling Intel that paraded Silvermont this year, sure it could have been a 14nm version but until now they'd have stuck with Silverthorne, blech. That IMO is the Intel without AMD.